Fig. 1. Rotational defects in eyes overexpressing Keren. (A-D) Sections through adult eyes (A,C), with schematics shown below (B,D). (A,B) In wild-type eyes, all ommatidia are orientated at precisely 90° to the equator. Dorsal and ventral ommatidia are of opposite chiral forms. (C,D) Eyes in which full-length keren is misexpressed under the control of sev-Gal4 (referred to as UAS-keren) show severe defects in rotational angle. All ommatidia, however, are of correct chiral form. In B and D, and all subsequent schematics, black trapezoids represent correctly orientated ommatidia, green trapezoids show underrotations, and blue trapezoids overrotations. The red line marks the position of the equator. In this and all images, anterior is to the left. (E) Confocal image and schematic of rotation in the third larval instar disc. (Left) Confocal projection of svp-lacZ/+ disc stained with -Elav (green) to mark photoreceptors and -ß-galactosidase (red) to highlight R1,3,4 and 6. The R3/R4 pair is initially parallel to the morphogenetic furrow (MF, arrowhead); ommatidia then undergo a fast 45° rotation, followed by a second, slower turn to 90°. Rotational positions are shown by white arrows. (Right) Schematic of the events occurring in left panel, showing rotation of, and recruitment of further photoreceptors to, the five-cell cluster.